The present invention provides an acid addition salt of 5-aminolevulinic acid or of a 5-ALA derivative with an acid which has a pKa of about 5 or less, preferably about 3 or less, with the proviso that the acid is other than hydrochloric acid. The magnet assembly provides an emanating magnetic field within which the drive coil is located. Each photo-sensing device has a structure adjusted to convert photons of the light to photoelectrons representative of a magnitude of the color component of the light for which the structure of the photo-sensing device is adjusted. They can be stopped in a timer mode for marking of any instant of time and after expiry of any time interval, for again synchronously running with the hands of the normal time display.